Symptoms of Weakness (loss of strength)

True weakness always interferes with function. Once a child is walking, weakness is seen more in the legs than the arms. Reason: muscle strength is needed for normal walking.

Leg Weakness. This is what you will see. Examples: trouble standing, walking, climbing stairs, getting off the floor, running and jumping. If severe, the child can't stand or walk.

Arm Weakness. This is what you will see. Examples: trouble feeding one's self, writing/drawing/typing, combing or washing the hair. Other children have trouble lifting objects above the head, turning door knobs or buttoning shirts. If the weakness is severe, the child starts dropping objects.

Weakness in Babies. In infants not yet walking, you will see the loss of motor milestones (loss of normal development). These include new trouble turning over, sitting, crawling, and pulling up. In the early months, you will see the loss of head support, reaching or kicking. A weak cry or suck also may be seen.

Causes of New Onset Muscle Weakness

Most causes of new onset muscle weakness are serious. True weakness points to diseases of the spinal cord or its nerves. Nerves carry messages from the spinal cord to the muscles in the arms and legs. Diseases that cause muscle weakness are very rare.

Most children with new onset weakness need special tests to make the right diagnosis. If the weakness gets worse, most children need to be admitted to the hospital.

Specific Causes of New Onset Muscle Weakness

Polio. A severe spinal cord disease that causes paralysis. It is prevented by the polio virus vaccine. Polio is almost wiped out in the entire world. There have been no cases in the US since 1979. Now, it only occurs in 2 countries.

Acute Flaccid Myelitis (AFM). A rare infection of the spinal cord. It acts like polio did. It causes sudden onset of arm or leg weakness in one or more places. The main cause has been an enterovirus. There has been a rise in cases since 2014.

West Nile Virus myelitis. See the Mosquito Bite care guide for details. Also acts like polio did.

Guillain-Barre syndrome. A severe nerve weakness that starts in the feet and moves up the body over several days. It affects the same parts on both sides of the body. It can follow some viral infections.

Tick paralysis. A rare problem from a tick that has been attached for 5 or more days. Often it is hidden in the hair. Once the tick is removed, the weakness clears. It takes a few hours to a day.

Poisoning. Some types of poisoning can cause weakness, often with confusion.

Viral myositis. Muscle pain in the leg muscles is seen with some viral infections, such as influenza. The pain can make some children not want to walk. This is different than weakness. The muscle pain lasts a few days to a week.